Firefighters have extinguished the fire. The unit has been destroyed and adjoining properties smoke affected.
Alternative accommodation is currently being arranged for affected residents.
Two ACT Fire & Rescue firefighters were involved in a flashover while inside the unit working to extinguish the fire. Their personal protective equipment (PPE) prevented them from suffering any serious injury. They were assessed on scene by intensive care paramedics for minor burns.
One of the firefighters is being transported to Calvary Hospital in a stable condition for observation with superficial burns to his hands.
A woman in 20's has also been taken to hospital due to the impact of smoke on her asthma condition.
The cause of the fire will be investigated.
ACT Fire & Rescue has three fire pumpers, the Bronto aerial platform, breathing aparartus support crew and commander on scene.